Cathode ray apparatus



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`v CATHODE RAY APPARATUS Filed Nov. 30, 1932 Mdc' JMrZoc/C, @yb-mou l" TTO/P/VEK mais July 9, 1935 -z,ot7,3so

.UNITED STATES PATENT OFFICE cA'rHonE RAY APPARATUS William J. Morlock, Collingswood, N. J., assignor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application November 3o, 1932, serial Ne. 644,931

2 claims. (ci. 25o-27.5)

My invention relates to improvements in cathat itis directed exactly at the center of the screen ode ray apparatus and the method of operating structure. the same. Further, in accordance with my invention, it

In some television systems, a cathode ray tube is proposed to utilize electromagnetic coils for 5 is utilized at the transmitting station to develop deflecting the ray in at least one direction, and 5 picture signals for transmission, and a cathode to supply to these coils a direct current of the ray tube is utilized at the receiving station to proper strength and polarity for the purpose of reproduce an image of the transmitted picture, vdirecting the undeflected ray to the center of under control of the picturesignals as received. the-screen structure.

The transmitting and receiving tubes are similar My invention resides in the apparatus and the 10 to the extent that each tube is provided with method of operation of the character hereinafter screen structure and with means in the form 'of described and claimed. an electron gun for developing a cathode ray and For. the purpose of illustrating my invention, for directing the same at the screen structure. an embodiment thereof is shown in the drawing,

Means in the form of electromagnetic coils or wherein 15 electrostatic plates are employed to deflect the Figure 1 is a perspective view, partly diagramray in different directions so that the same is matic, of cathode ray apparatus embodying my caused to scan the screen structure over a definite invention; and

pattern, usually a square or rectangular portion Figs. 2, 3 and 4 are diagrammatic viewsl illusof the screen structure. trative of several modifications. 20

In making these tubes, it is attempted to make In Fig. 1, the reference numeral l0 designates the axis of the electron gun exactly in line and a cathode ray tube of the usual type employed at coincident with the axis of the tube, so that the a television receiving station for reproducing an undeflected ray is directed exactly at the center image of the transmitted object. This tubeisproof the screen structure. When this condition is vided, at one end thereof, with fluorescent screen 25 obtained, the center of the pattern over which structure I2, and at its other end with a suitable the ray scans the screen structure is exactly at electron gun Il for developing a cathode ray I6 the center of the latter. In this connection, howand directing the ray at the Screen Structure. ever, the construction is not always perfect as For the purpose of causing the ray to scan'the l regards the lining-up of the electron gun. The screen structure over a rectangular area or pat- 30 result is that the undeflected ray is directed to tern I8, electromagnetic coils 20 are utilized to a spot on the screen structure substantially reperiodically deflect the ray hOIiZOntally and elecmoved from the center thereof. When the rayis tromagnetic coils 22 are utilized to periodically dedeflected, therefore, the center of the area. flect the ray vertically.

scanned is off to one side a substantial amount, If, in the construction of the tube, the axis of 35 and in some cases the discrepancy is so great the gun I4 is unintentionally made slightly out of that the ray scans the side wall of the tube along line with the axis of the tube, the undei'lected one or more edges of the pattern. y ray will be directed at a spot on the screen struc- With the foregoing in mind, it is one of the ture substantially removed from the center 24. 40 objects of my invention to provide improved The area actually scanned will then be shifted 40 cathode ray apparatus and an improved method substantially from the desired area I8. In one of operating the same whereby the cathode ray forni of my invention, this conditionk is corrected can be caused to scan the screen structure over for by winding a few turns of wire around the coils a pattern whose center is coincident with the cen- 20 to provide the auxiliary series-connected coils ter of the screen structure, regardless of any 26. Similarly, a few turns of wire are wound 45 faulty construction whereby the axis of the elecaround the coils 22 to provide the auxiliary seriestron gun is out of line with the axis of the tube. connected coils 28.

Other objects and advantages will hereinafter In operation, the coils 20 and 22 are connected to appear. suitable electrical circuits for causing current In accordance with my invention, a fixed auxwaves of the proper shapes and frequencies to 50 iliary :field is developed which is independent of pass through these coils. the ray-deflecting'fleld and is substantially sym- The auxiliary coils 26 and 28 are excited from a metrlcal with respect to the undeflected ray, and suitable source 30 of direct current, through conthe eld is so adjusted that the undeected ray nections 32 and 34 connected, as shown, to the Y is centered or brought back to the position whereoutside ends of these coils. The degree of exci- 55 2 aoovgsso tation of the coils 26 and 28 is controlled, respectively, by rheostats 36 and 38, each of the latter having a relatively high resistance value. The connections to the auxiliary coils 26 and 28 are made to give the proper polarities so that, when current is caused to flow-through these coils, the undeiiected ray is deilected downwardly or upwardly, and/or to the right or the left, as might be required to direct the ray at the center spot 24 of the screen structure. fiection of the ray is controlled by adjustment of the rheostats 36 and 38.

By the means just described, a fixed auxiliary magnetic field, independent of the ray-deilecting field, and substantially symmetrical to the undeflected ray, is developed, and the ray is caused to pass through this auxiliary field during the normal scanning action under the influence of the raydefiecting coils 28 and 22.

In the embodiment of my invention just described, the auxiliary coils 26 and 28 may be wound on separate pole pieces if there is not sufficient room to accommodate them on the ray-deflecting coils 28 and 22.

In Fig. 2 is shown a modication wherein the ray-deiiecting coils 28 and 22 also are utilized for centering the undeilected ray. In this case, alternating-current-supply connections 48 and 42 are provided for supplying to the coils 28 and 22, respectively, current waves of the proper shapes and frequencies to cause the ray I6 to scan the area or pattern I8. Direct-current-supply connections 32a and 34a, corresponding to the connections 32 and 34 in Fig. l, are connected to the outside ends of the coils 28. For the purpose of preventing the alternating current from entering the direct current voltage supply, coils 44 and 46, each of relatively high impedance, are disposed in and form part of the connections 32a and 34a, the A. C. connections 48 being connected between these impedance coils and the coils 28. A rheostat 48 is provided for controlling the amount of direct current component in the coils 28, and serves the same purpose as the rheostat 36 in Fig. 1.

The connections to the coils 22 are the same as those of the coils 28, the rheostat 58 serving the same purpose as the rheostat 38 in Fig. 1.

In operation, the polarities of the direct current sources 38a and 38b are made such that the undeilected ray is deflected in the proper directions to direct the same at the center spot 24 of the screen structure, and the rheostats 48 and 58 are adjusted to control the amount of deflection.

In Fig. 3, the operation is the same as in Fig. 2, except that condensers 52 and 54 are disposed between the alternating-current-supply connections 48 and 42 and the direct-current-supply connections to prevent the alternating current generator from short-circuiting the direct current source.

Fig. 4 illustrates another embodiment of my The amount of such de invention wherein the deilecting coils are used for centering the ray, as in Figs. 2 and 3. In this case, however, the direct-current supply is taken from a potentiometer 56 connected as shown between ground and the high potential end of a shunt feed reactor 68 connected ln the plate circuit of an output tube 68 forming part of a deiiecting circuit 62. This circuit, as is well known, operates to supply to the coils 28 a current wave of the proper form and frequency. The power supply end of the reactor 58 is at a higher direct current potential than the plate end thereof, so that current will iiow through the defiecting coils in the correct direction to center the ray I6. The ground end of the coils 28 is connected to the adjustable contact 64 of the potentiometer, and by adjusting this contact, direct current can be made to ow through the coils to the plate of the tube 68, or from this plate through the coils. The undefiected ray, therefore, can be deflected in either direction, as might be required to direct the same at the center spot 24.

Since the potentiometer 56 might offer an undesirable impedance to the alternating deflecting currents, the ground end of the defiecting coils is connected to ground through a by-pass condenser 66.

The same connections shown in Fig. 4 can be used for the vertical defiecting coils 22. That is, the voltage drop across the shunt feed reactor in the deection circuit for these coils is utilized in the same manner to cause the centering current to pass through the coils 22.

Various other modiiications, within the conception of those skilled in the art, might be made without departing from the spirit of my invention or the scope of the claims.

I claim as my invention:

1. In combination, a cathode ray tube having screen structure and an electron gun for directing a cathode ray toward said structure, a yoke member surrounding the tube intermediate the gun and the screen structure and lying in a plane substantially normal to the axis of the electron gun, the said member having four extensions of magnetically permeable material directed inward toward the tube and spaced apart circumferentially thereof substantially ninety degrees, a plurality of coils, at least one coil on each extension, each coil being connected in series-aiding relation to an opposite coll, terminal connections for supplying the coils with fluctuating currents for ray deflection purposes, and terminal connections for supplying the coils with unidirectional current whereby the locus of the scanning pattern of the ray on the fluorescent screen may be adjusted.

2. The invention set forth in claim 1, characterized in that the yoke member is also magnetically permeable.

WILLIAM J. MORLOCK. 

